The present invention relates to a damping system for a washing machine, and more particularly to the system which controls the vibrations generated at a tub by rotation of a suit basket using an active damping device.
In general, an active damping system is a control system which attenuates vibration by forcing a control force against the vibration generated nonlinearly and randomly in a mechanical device, or a wing of an airplane and so on.
During the washing and dehydrating, operation of a conventional washing machine, the tub vibrates during rotation of the suit basket, and because the suit basket rotates counterclockwise during dehydrating operation, the vibration of the tub is greater during dehydrating operation. At this time, the amplitude of the vibration is dependent on the unbalance of the weight of the laundry. Accordingly, when the suit basket rotates it is slanted due to the unbalance of the weight of the laundry, and it collides with the tub. The washing machine does not perform correctly and it makes a low frequency noise due to the excessive vibration.
In order to solve the problem, such a mechanical assembly such as an elastic spring or a rubber member has been attached to the upper face of the tub in the conventional washing machine. However, the mechanical assembly has a complicated structure, and when a vibration of the suit basket is nonlinear and random, the mechanical assembly does not effectively control the vibration.
The typical example to solve the problem is disclosed in Japanese Utility Model Laid-Open Sho 54-124360. This invention does not generate an effective control force which is equal to the amplitude of the vibration and having the opposite direction. Also, because it performs a damping operation with a pair of permanent magnets, it does not generate a control force stronger than a particular force.